The present invention relates to a novel cleaning and preservative solution for contact lenses. More particularly, it relates to a solution which can be used for cleaning contact lenses as well as for preserving contact lenses.
Heretofore various kinds of contact lenses have been used. As typical contact lenses there are water-nonabsorptive contact lenses made of polymethyl methacrylate or silicone rubber and water-absorptive contact lenses made of predominantly poly-2-hydroxyethyl methacrylate or polyvinyl pyrrolidone.
Recently there have been also proposed water-nonabsorptive hard contact lenses having an oxygen permeability which are made of materials such as poly-4-methylpentene-1 (see Japanese Patent Publication No. 22320/1972), cellulose acetate butyrate (see U.S. Pat. No. 3,900,250) and a copolymer of (polysiloxanyl)alkyl methacrylate and methyl methacrylate (see Japanese Patent Publication No. 33502/1977).
When those contact lenses, particularly water-nonabsorptive contact lenses are worn on eyes, their surfaces are contaminated mainly by sebum being a secretion in eyes. For this reason, the contact lenses removed from eyes should be cleaned immediately to remove the contamination such as sebum fixed to the surfaces thereof. The wear of insufficiently cleaned contact lenses results in a great cause for uncomfortable symptoms such as foggy sight, pain and ocular injection.
A usual method adopted for cleaning contact lenses is that in which a cleaning solution containing a salt of a polyoxyethylene higher alkyl ether sulfuric acid ester is applied to both surfaces of contact lenses and the surfaces are then rubbed with fingers. The contact lenses cleaned are rinsed with a running water or a physiological saline solution and then stored in a preservative solution containing ingredients such as sodium chloride, a buffer and a bactericide. The storage of the contact lenses in the preservative solution is important, particularly as to the water-absorptive contact lenses, to maintain them in a hydrous state. With the water-nonabsorptive contact lenses, it is also preferable to store them in the preservative solution in order to maintain the surfaces of the lenses in a hydrophilic state, to reduce a foreign body sensation when the lenses are worn on eyes and to store the lenses sanitarily so that they are ready in a clean state for the next wear.
In a conventional use of contact lenses, the cleaning and preservation of contact lenses are carried out separately with using different cleaning and preservative solutions, which requires a considerably troublesome labor.
The conventional use has an another disadvantage that the surfaces of contact lenses are damaged in the cleaning thereof since the lenses are rubbed with fingers. Particularly the oxygen-permeable hard contact lenses tend to be damaged more readily since generally they have a poor surface hardness in comparison with the common hard contact lenses made of polymethyl methacrylate. In case of contact lenses made of a water-repellent or hydrophobic material such as silicone rubber, they are sometimes subjected to a treatment for making the surfaces thereof hydrophilic such as applying a corona discharge to the surfaces of graft-copolymerizing a hydrophilic monomer such as 2-hydroxyethyl methacrylate to the surfaces for the purpose of improving the affinity of the lenses to cornea. When such treated contact lenses are washed by rubbing with fingers, the surfaces made hydrophilic are damaged, which results in the decrease of the lifetime as contact lenses.
In case of cleaning contact lenses by rubbing with fingers, there frequently occurs an unforeseen accident that the lenses slip out of the fingers and are missing.
The cleaning solution for the water-nonabsorptive contact lenses is prepared in many cases with paying no regard to the safety against ocular tissues since the material of the lenses is water-nonabsorptive. Therefore, when the contact lenses which are not rinsed sufficiently after cleaning or in which some ingredients of the cleaning solution still remain after rinse are worn on eyes, an accident that the eyes are irritated occurs. Furthermore, such a serious accident tends to occur that the cleaning solution is used erroneously instead of a wetting agent which is applied to the surfaces of the water-nonabsorptive lenses in wearing thereof in order to improve the hydrophilic property of the surfaces thereof and the ocular tissues are damaged fatally.
When the previously mentioned conventional cleaning solution containing a chemical such as a salt of a polyoxyethylene higher alkyl ether sulfuric acid ester as a main ingredient for water-nonabsorptive contact lenses is used for cleaning the above-mentioned water-nonabsorptive contact lenses of which surfaces are treated to become hydrophilic or water-nonabsorptive contact lenses having a hydrophilic surface as described in the same assignee's U.S. Patent Application Ser. No. 944,843, the main ingredient of the cleaning solution tends to be adsorbed onto the hydrophilic surfaces of the contact lenses. Since the adsorbed ingredient is not removed readily by rinsing the lenses with a running water, the adsorption of the ingredient of the cleaning solution is not suitable from a viewpoint of safety against ocular tissues and further the hydrophilic property of the lens surfaces is sometimes hindered by the adsorbed ingredient, by which the proper functions of contact lenses are influenced badly.